Use more SPI CS from GPIO

fvllml
fvllml New Member Posts: 7

Hello, I want to have 8 CS from the Up squared board. I have done it for Raspberry Pi by following this link but cannot find a good tutorial for Up squared. I'm using ubuntu 20.04 with the RT patch.

Linux up 5.4.65-rt38+ #1 SMP PREEMPT_RT Mon Feb 28 13:42:31 CET 2022 x86_64 x86_64 x86_64 GNU/Linux

Have someone managed to program more CS on the Up squared? any idea how could I do that?

Thanks

Comments

  • fvllml
    fvllml New Member Posts: 7

    So I managed to create a new spidev device with ACPI overlays as follows:

    /*
     * This ASL can be used to declare a spidev device on SPI0 CS2
     */
    DefinitionBlock ("", "SSDT", 5, "INTEL", "SPIDEV2", 1)
    {
        External (_SB_.PCI0.SPI1, DeviceObj)
        External (_SB_.PCI0.GIP0.GPO, DeviceObj)
    
        Scope (\_SB.PCI0.SPI1)
        {
    
            Name (_CRS, ResourceTemplate () {
                GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionOutputOnly,
                    "\\_SB.PCI0.GIP0.GPO", 0) {
                        22 // pin 22 is BCM25 or 402 in linux
                    } 
            })
    
            Name (_DSD, Package() {
                ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
                Package () {
                    Package () { "compatible", "spidev" }, // not sure if this is needed
                    Package () {
                        "cs-gpios", Package () {
                            0,
                            0,
                            ^SPI1, 0, 0, 0, // index 0 in _CRS -> pin 22
                        }
                    },
                }
            })
    
            Device (TP2) {
                Name (_HID, "SPT0001")
                Name (_DDN, "SPI test device connected to CS2")
                Name (_CRS, ResourceTemplate () {
                    SpiSerialBus (
                        2,                      // Chip select
                        PolarityLow,            // Chip select is active low
                        FourWireMode,           // Full duplex
                        8,                      // Bits per word is 8 (byte)
                        ControllerInitiated,    // Don't care
                        1000000,                // 10 MHz
                        ClockPolarityLow,       // SPI mode 0
                        ClockPhaseFirst,        // SPI mode 0
                        "\\_SB.PCI0.SPI1",      // SPI host controller
                        0                       // Must be 0
                    )
                })
            }
        }
    }
    
    

    However, the CS on pin 22 is low all the time which shouldn't be the case. Perhaps I need to enable the GPIO somehow? is the number of the pin correct? I'm using pin numbering from here